1. Field of the Invention
The present invention relates to a method for determining metal voids for semiconductor devices. In particular, the present invention relates to a method for categorizing semiconductor wafers based on size of metal voids in those wafers, by using two different parameters obtained from isothermal testing of wafers.
2. Description of the Related Art
Isothermal testing is performed on semiconductor wafers in order to determine the reliability of those wafers, in particular the reliability of the metal system of a semiconductor device. Isothermal testing involves accelerated stressing of a test line, where the average temperature of the test line is raised to a target temperature through joule heating. For example, a semiconductor wafer is exposed to joule heating at an accelerated temperature, to determine if the wafer is faulty.
At present, there are no accurate methods for categorizing a wafer based on the size of voids formed therein, without having to cut up the wafer and to analyze the wafer under a scanning electron microscope (SEM).